\subsection{Calcolo del determinante}
\(
\left|
\arraycolsep=1.5pt\def\arraystretch{1.0}
\begin{array}{cccc}
2 & 0 & -2 & 1 \\
3 & \circled{1} & 3 & 4 \\
-1 & \circled{2} & 0 & 2 \\
1 & 0 & 1 & -1 \\
\end{array}
\right|
=
1 (-)^4
\left|
\arraycolsep=2.0pt\def\arraystretch{1.0}
\begin{array}{ccc}
2 & -2 & 1 \\
-1 & 0 & 2 \\
1 & 1 & -1 \\
\end{array}
\right|
+ 2 (-)^5
\left|
\arraycolsep=2.0pt\def\arraystretch{1.0}
\begin{array}{ccc}
2 & -2 & 1 \\
3 & 3 & 4 \\
1 & 1 & -1 \\
\end{array}
\right|
=
(0-1-4-0+2-4) -2(-6-8+3-3-8-6) = 49
\)
